Vibration wave driven motor

ABSTRACT

A vibration wave driven motor having an electromechanical energy conversion member for generating a vibration wave in an elastic member. This conversion member has first and second surfaces opposite to each other, and first and second surfaces respectively formed on the first and second electrodes to receive an applied electrical signal. The first electrode is formed in a position such as to face one side of the elastic member and has an electrical signal input terminal provided on the second surface side of the conversion member. This input terminal and the first electrode are electrically connected by, for example, a conductor formed in a through hole. It is thereby possible to supply an electric current to each electrode with reliability while maintaining the conversion member and the elastic member in desired close contact with each other.

The present application is a division of application Ser. No.08/086,374, filed Jul. 6, 1993, which is a continuation of applicationSer. No. 07/699,008, filed May 13, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a vibration wave driven motor in which amovable member is frictionally driven by a vibration member and, moreparticularly, to the structure of an electricity supply means for such amotor.

2. Description of the Related Art

Vibration wave driven motors, in which a vibrational motion of anelectro-mechanical energy conversion element such as a piezoelectricelement caused-when an alternating wave voltage is applied to theelement is converted into a rotational motion or one-dimensional motion,have a simpler structure and a smaller size in comparison withconventional electromagnetic motors because they require no coilwinding. Also, they are capable of obtaining a large torque even at alow rotational speed. They have attracted attention in recent yearsbecause of these advantages.

FIGS. 9 and 10 show the principle of driving of a vibration wave drivenmotor, and FIG. 9 shows vibration waves generated in a vibration memberof the motor. Piezoelectric elements 2a and 2b, arranged into apiezoelectric plate 2, form electro-mechanical energy conversionelements and are bonded to a vibrating member 1 (ordinarily, a metallicmember). Elements 2a and 2b are arranged in positions relatively shiftedλ/4 where λ is the wavelength in the vibrating member. The piezoelectricelements 2a and 2b and the vibrating member 1 constitute a stator.

In the case of a conventional motor, a common electrode is provided onone of two surfaces of each of piezoelectric elements 2a and 2b incontact with the vibrating member 1 which is conductive, and anelectrode is provided on the other surface of each piezoelectric element2a or 2b. Each element is previously polarized as indicated by ⊕ and ⊖in FIG. 9. An AC voltage of V=Vosin(Ωt±π/2) is applied to thepiezoelectric element 2a from an AC power source 3a, while an AC voltageof V=Vosin(ωt±π/2) phase-shifted by π/2 is applied to the piezoelectricelement 2b through a 90° phase shifter 3b. (+) and (-) in the aboveequation are changed over by the phase shifter 3b according to thedirection in which the movable member 6 is moved. It is assumed herethat (-) is selected and that a voltage of V=Vosin(ωt-π/2) is beingapplied to the piezoelectric element 2b. If the piezoelectric element 2ais oscillated alone by the voltage V=Vosin ωt, vibration of a standingwave such as that shown in (a) of FIG. 9 occurs. If only thepiezoelectric element 2b is oscillated by the voltage V=Vosin (ωt-π/2),vibration of a standing wave such as that shown in (b) of FIG. 9 occurs.When these two AC voltages out of phase with each other aresimultaneously applied to the piezoelectric elements 2a and 2b, thevibration wave becomes a traveling wave. A wave shown in (A) of FIG. 9is exhibited at a time t=2nπ/Ω, a wave in (B) is exhibited at a timet=π/2ω+2nπ/ω, a wave in (C) is exhibited at a time t=π/ω+2nπ/ω, and awave in (D) is exhibited at a time t=3π/2ω+2nπ/ω. The wave front of thevibration wave advances in the direction x (FIG. 10).

This traveling vibration wave involves a longitudinal wave and atransverse wave. As shown in FIG. 10, with respect to a mass point A ofthe vibrating member 1, a counterclockwise revolving ellipsoidal motiondefined by the longitudinal amplitude u and the transverse amplitude wis caused. A movable member 6 is maintained in contact with the surfaceof the vibrating member 1 by being pressed against the same. The movablemember 6 contacts the vibrating member 1 at the apexes of the vibratingsurface alone. (Actually, it contacts vibrating member surfaces of acertain width in the wave travel direction). The movable member 6 isdriven by the longitudinal amplitude u component of the ellipsoidalmotion of mass points A, AA, . . . at the apexes to move in thedirection of the arrow N. When the 90° phase shifter shifts the phase by+90°, the vibration wave travels in the direction -x, and the movablemember 6 moves in the direction opposite to the direction N.

The AC voltage applied to such a vibration wave motor must be highenough to move the movable member 6, ordinarily several ten volts p--por higher. Accordingly, for use in a small apparatus using ordinary drybatteries on the market, a means for boosting the voltage, e.g., atransformer is required.

To cope with this problem, the applicant of the present invention hasalready proposed a vibration motor having a stator constructed as shownin FIG. 11 (Japanese Patent Laid-Open No.59-96882). That is, theconductive vibrating member 1, an electrode 8A on the vibrating memberside of the piezoelectric element 2a (hereinafter referred to as reverseelectrode 8A), and an electrode 9A on the vibrating member side of thepiezoelectric element 2b (hereinafter referred to as reverse electrode9A) are electrically insulated from each other by insulating layer 7,and an AC voltage which is provided by inverting the AC voltage appliedto electrodes 8, 9 on the side remote from the vibrating member(hereinafter referred to as obverse electrodes 8, 9) is applied to thereverse electrodes 8A, 9A. Theoretically, the same function andperformance can be achieved by applying to this motor an AC voltagewhich is half the voltage required in the arrangement shown in FIG. 9.The insulator 7 which electrically insulates the reverse electrode 8Aand 9A and the vibrating member 1 is unnecessary if the vibrating member1 is not electrically conductive.

In the arrangement of FIG. 11, however, the thickness of the reverseelectrodes 8A and 9A is very small (1 μm or less) and it is thereforevery difficult to apply AC voltages through end surfaces of the reverseelectrodes.

Lead wires or flexible print plates or the like may be interposedbetween the reverse electrodes 8A and 9A to enable application of ACvoltages to the reverse electrodes 8A and 9A. In this case, however,close contact between the vibration member i and the piezoelectricelement 2 is impaired, resulting in a deterioration in motorperformance, e.g., a reduction in efficiency.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a vibration motor inwhich electric energy can be supplied to each piezoelectric element withimproved reliability.

It is another object of the present invention to provide a vibrationmotor in which each piezoelectric element and the elastic vibratingmember can be maintained in desired close contact with each other.

In one aspect, the invention provides a vibration member for a vibrationwave driven motor comprising an electro-mechanical energy conversionmember having a first surface and a second surface opposite thereto, avibration member adjacent the first surface, first and second electrodesformed respectively on the first and second surfaces of the conversionmember, a third electrode formed on the second surface of the conversionmember, and an electrical conductor for electrically connecting thefirst electrode and the third electrode.

Other objects of the present invention will become clear from thefollowing detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a to 1c show a vibration wave motor in accordance with anembodiment of the present invention;

FIG. 1a is a cross-sectional view of the stator;

FIGS. 1b and 1c are diagrams of an electrode pattern on thepiezoelectric element;

FIGS. 2a to 2c are diagrams of a modification of the embodiment shown inFIGS. 1a to 1c;

FIGS. 2a and 2b are diagrams of an electrode pattern;

FIG. 2c is a cross-sectional view taken along the line II--II of FIGS.2(a) and 2(b);

FIGS. 3a to 3h are diagrams of a process of manufacturing the stator ofthe embodiment shown in FIG. 1;

FIGS. 4a to 4e are diagrams of another stator manufacturing process;

FIGS. 5 and 6 are an exploded perspective view and an electrode patterndiagram, respectively, of a second embodiment of the present invention;

FIGS. 7 and 8 are an exploded perspective view and a perspective view,respectively, of a third embodiment of the present invention;

FIG. 9 is a schematic diagram of a conventional vibration motor;

FIG. 10 is a diagram of the principle of driving of the vibration motor;and

FIG. 11 is a schematic diagram of another conventional vibration motor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Features of the present invention are shown in FIGS. 1a to 1c. FIG. 1ais a developed view of a section of the stator cut in thecircumferential direction, FIGS. 1b and 1c are diagrams of the reversesurface (on the vibrating member 1 side) and the obverse surface of apiezoelectric element 2, e.g., a PZT ceramic element connected to anelectrically conductive elastic vibrating member 1 and an insulator 7.For convenience, FIG. 1c shows a mirror image of the actual pattern. Agroup of electrodes 81 to 85 formed by, for example, depositing a metalor applying a conductive paste are provided for one group 2a of twogroups of piezoelectric elements 2a and 2b. A reverse electrode 8A ofthe group of elements 2a is grounded. Plus and minus voltages areapplied to the group of electrodes 81 to 85 by being alternativelydistributed so that the group of elements 2a are polarized as indicatedby ⊕ and ⊖ in FIG. 1a. After polarization, conductive members 86 forconduction between the group of electrodes 81 to 85 are formed by, forexample, applying a conductive paste, thereby forming an obverseelectrode 8 of the group of piezoelectric elements 2a in which the groupof electrodes 81 to 85 are electrically connected and which is connectedto a lead wire 87.

A through hole 10 is formed through the layer of piezoelectric elements,and a conductive member 18 is formed on the inner surface of the throughhole 10 by, for example, plating to electrically connect the reverseelectrode 8A of the group of piezoelectric elements 2a and a reverseelectrode 28 provided on the obverse side (hereinafter referred to as"obverse-side reverse electrode"). A lead wire 87A is connected to theobverse-side reverse electrode 28 and is, of course, conductive to thereverse electrode 8A. The electrodes and conductor members on thepiezoelectric element group 2a side are thus provided. Also, theelectrodes and conductive members of the other group of piezoelectricelements 2b are provided in the same manner, the group of piezoelectricelements 2b being located at a distance of 3/4 wavelength in terms ofphase from the group of piezoelectric elements 2a. Members 91 to 97,97A, 9, 9A, 11, 19 and 29 of the group of piezoelectric elements 2b arethe same as in principle the groups of electrodes 81 to 85, conductivemembers 86, lead wires 87 and 87A, obverse electrode 8, reverseelectrode 8A, hole 10, conductive member 18, and obverse-side reverseelectrode 28 of the group of piezoelectric elements 2a. The componentsof this arrangement indicated by the same reference characters as thoseshown in FIGS. 9 to 11 have the same functions. In the thus-constructedstator, a voltage of V=1/2Vosinωt is applied to the obverse electrode 8of the group of piezoelectric elements 2a from an AC power source 3athrough the lead wire 87, a voltage of V=1/2Vosin(ωt+π) is applied tothe reverse electrode 8A through a 180° phase shifter 3c and the leadwire 87A, a voltage of V=1/2Vosin(ωt±π/2) is applied to the obverseelectrode 9 of the other group of piezoelectric elements 2b through a90° phase shifter 3b and the lead wire 97, and a voltage ofV=1/2vosin(ωt±3π/2) is applied to the reverse electrode 9A of the othergroup of piezoelectric elements 2b through a 180° phase shifter 3d andthe lead wire 97A. (+) and (-) in the above equations are changed overby the phase shifter 3b according to the direction in which the movablemember (not shown) which is known per se is moved. It is assumed herethat (-) is selected and that the voltages of V=1/2Vosin(ωt-π/2) andV=1/2Vosin(ωt-3π/2) are being applied to the obverse electrode 9 and thereverse electrode 9A of the group of piezoelectric elements 2b,respectively. If the voltages of V=Vosinωt and V=Vosin(ωt-3π/2) arebeing simultaneously applied respectively to the obverse electrode 8 andthe reverse electrode 8A of the group of piezoelectric elements 2a, atraveling vibration wave in the direction x is generated as in the caseof the conventional vibration motor shown in FIG. 9. The principle oftraveling of the movable member is the same as that described above withreference to FIG. 10 with respect to the conventional vibration wavemotor. In this embodiment, it is preferable to set the frequency of theAC voltage to a frequency close to the out-of-plane sixth deflectionmode frequency, because the amplitude of vibration of the vibratingmember 1 is increased at this frequency.

In this embodiment, if the same AC power source 3a as that for use withthe conventional vibration motor shown in FIG. 10 is used, the electricfield produced at each of the piezoelectric elements 2a and 2b is twiceas large as that in the case of the conventional motor, because the ACvoltage 180° out of phase with the AC voltage applied to the obverseelectrode is applied to the reverse electrode. That is, an AC powersource the voltage level of which is half that required by theconventional vibration motor shown in FIG. 9 can be used to obtain thesame amplitude of the vibrating member, torque and rotational speed asthe conventional vibration motor.

In the structure of this embodiment, obverse-side reverse electrodes 28and 29 are provided so that voltages can be applied to reverseelectrodes 8A and 9A from the obverse side. It is thereby possible tosupply power as desired while maintaining the vibrating member 1, theinsulator 7 and piezoelectric element 2 in close contact with eachother.

In the above-described embodiment, the electrode or polarization patternprovided on the piezoelectric element 2 has the same pitch as theout-of-plane sixth deflection mode. However, it may alternatively have apitch equal to the pitch of a difference natural vibration mode. A modesuch as one including a node in the circumferential direction is alsopossible. The present invention is effective with respect to allvibration motors in which electrodes are provided on the bonding side ofthe piezoelectric element and in which the vibrating member and theseelectrodes are insulated from each other.

In the above-described embodiment, the groups of piezoelectric elements2a and 2b form one piezoelectric member 2. However, in other cases wherepiezoelectric elements are formed as separate piezoelectric members orwhere groups of piezoelectric elements form a plurality of piezoelectricmembers, each reverse electrode can be electrically connected to anobverse surface region (obverse-side reverse electrode) through aconductive member formed on a surface generally perpendicular to thepiezoelectric element surface to apply a voltage from the obverse-sidereverse electrode.

In the above-described embodiment, the surface generally perpendicularto the piezoelectric element surface is provided as the through holesurface. However, it is not limited to the through hole surface and maybe formed as a piezoelectric element end surface, as shown in FIGS. 2a,2b, and 2c.

Preferably, at least portions of the conductive members 18 and 19bordered on the reverse electrodes, which conductive members 18 and 19are formed on the surfaces generally perpendicular to the piezoelectricelement surfaces, are formed before the step of bonding thepiezoelectric member 2 and the vibrating member 1. A process in whichthese portions are formed will be described below with reference toFIGS. 3a to 3h. Vibrating member 1 to be bonded to piezoelectric member2 undergoes the step of providing insulator 7 as shown in FIG. 3b (whichstep is unnecessary if the vibrating member 1 is formed of an insulatingmaterial), and the bonding surface is polished in the step of FIG. 3c toenable desired close contact. This polishing is unnecessary if thevibrating member 1 has already been polished on its bonding side andprovided that the insulator is formed uniformly by the step of FIG. 3b.For example, polishing in the step of FIG. 3c is unnecessary in a casewhere the vibrating member 1 is formed of aluminum (Al) and is polishedon its bonding side in the step of FIG. 3a, and where an alumite layerhaving a thickness of several microns to several ten microns is formedby anode oxidation or the like in the step of FIG. 3b. Piezoelectricelements are bonded to the thus-provided vibrating member covered withthe insulator, as described below. In the step of FIG. 3d, piezoelectricceramic 2 (2a), e.g., PZT, is formed and sintered and the bondingsurface of this ceramic member is polished to enable desired closecontact. In the step of FIG. 3e, obverse electrodes 81 to 85, reverseelectrode 8A portion 18A of conductive member 18 formed on the internalsurface of hole 10 which portion 18A is bordered on reverse electrode 8Aobverse-side reverse electrode 28 are formed as polarizing electrodes bydeposition of a metal, screen printing of a conductive paste or othermethods. If the portion 18A is formed by depositing a metal, depositedmolecules are made to move round to the hole 10 surface at the time offormation of the reverse electrode 8A. If a conductive paste is formedby screen printing, the conductive paste is made to flow into the hole10 surface so as to partially cover the same. Thus, in either case, theportion 18A can be formed at the time of formation of reverse electrode8A; it can be provided without making the process complicated.Polarization is effected by using the electrodes formed in this manner.In the step of FIG. 3f, the obverse electrodes 81 to 85 are connected byconductive members 86 to form obverse electrode 8. The piezoelectricceramic member on which polarized electrodes are formed in this manneris bonded (in the step of FIG. 3g) to the vibrating member with theinsulator processed by the steps of FIGS. 3a to 3c. Finally, aconductive member is formed on the internal hole surface by, forexample, the method of applying the conductive paste to the hole surfaceto establish electrical connection between the reverse electrode 8A andthe obverse-side reverse electrode 28. In a case where the portion 18Aof the conductive member on the hole surface bordered on the reverseelectrode 8A is not formed in any step before the bonding step, andwhere the conductive member is bonded to the hole surface, it is verydifficult to electrically connect the conductive member 18 on the holesurface to the reverse electrode 8A because the thickness of the reverseelectrode 8A is very small (e.g., ordinarily 1 μm or less if thiselectrode is formed by deposition). However, if a process step such asthat shown in FIG. 3 is conducted, the electrical connection can beestablished therebetween with reliability without requiring acomplicated process. Also the conductive member 18 can be formed so asto ensure the desired close contact between the bonding surfaces.

In the process shown in FIG. 3, the conductive member 18 is formed onthe hole inner circumferential surface alone. However, it may be formedso as to completely close the hole in the step of FIG. 3h. Although theformation of only the group of piezoelectric elements 2a has beendescribed with reference to FIG. 3, the other group of piezoelectricelements 2b can be formed by the same process.

Another process of forming the conductive member formed on the surfacegenerally perpendicular to the piezoelectric element surface will bedescribed below with reference to FIGS. 4a to 4e. First, as shown inFIG. 4a, piezoelectric ceramic 2 such as PZT is formed and sintered withconductive members 18 and 19 previously embedded therein. The sinteredblock is sliced into flat pieces, and bonding surfaces of the slicedpieces are polished to enable desired close contact (step of FIG. 4b).Thereafter, obverse electrodes 81 to 85, and 91 to 95, reverseelectrodes 8A and 9A, obverse-side reverse electrodes 28 and 29 areformed by, for example, deposition on each piezoelectric member,followed by polarization. Further, conductive members 86 and 96 areprovided to form obverse electrodes 8 and 9 (step of FIG. 4d). The sameprocess steps as those of FIGS. 3a to 3c are thereafter conducted, andthe piezoelectric member is bonded to the vibrating member 1 to whichinsulator 7 is attached (step of FIG. 4e). The conductive membersembedded before sintering establish reliable electrical connectionsbetween the reverse electrode 8A and the obverse-side reverse electrode28 and between the reverse electrode 9A and the obverse-side reverseelectrode 29. Since in the step of FIG. 4b the bonding surface of thepiezoelectric ceramic member formed is polished, the vibrating member 1and the insulator 7 can be maintained in desired closed contact witheach other. The material of the conductive members 18 and 19 is,preferably, a stable material which is not changed in conductiveproperties by being melted at the sintering temperature, or by beingdiffused or oxidized, because it is fired together with thepiezoelectric ceramic. For example, PZT which is a piezoelectric ceramicis ordinarily sintered at a temperature of 1100° to 1200° C. and, if PZTis used, gold wires, silver paste, silver-palladium alloy or the likemay preferably be used. In the process shown in FIGS. 4a to 4e, thepiezoelectric ceramic is formed into a cylindrical shape and sintered inthis form. However, conductive members 18 and 19 can be formed in thesame manner in the case of other forming methods, e.g., a sheet formingmethod in which a sheet member is punched out and sintered. In thiscase, conductive members may be embedded simultaneously with or beforeor after punching and sintering may thereafter be effected.

As described above with reference to FIGS. 3 and 4, at least a portionof the conductive member formed on the surface of the piezoelectricmember generally perpendicular to the bonding surface of the same whichportion is bordered on the reverse electrode is formed before bonding,thereby enabling reliable electrical connection between the reverseelectrode and the obverse-side reverse electrode as well as desiredclose contact between the piezoelectric member and the vibrating member.

FIG. 5 shows another embodiment of the present invention wherein thepresent invention is applied to a vibration wave motor in which twolayers of piezoelectric ceramic are superposed on each other. Thepiezoelectric ceramic is laminated to obtain the same performance whilefurther reducing the AC voltage in half again; the same performance canbe obtained by an AC voltage which is 1/4 the voltage required by theconventional vibration wave motor in which piezoelectric elements andelectrodes are arranged as shown in FIG. 9. A piezoelectric ceramicmember 2ab is bonded to vibrating member 1 on which insulator 7 isprovided, and another piezoelectric ceramic member 2abb is bonded to thepiezoelectric member 2ab. The electrode pattern of the piezoelectricceramic member 2ab on the vibrating member side (hereinafter referred toas reverse side) is as illustrated in FIG. 5, and is the same as theelectrode pattern of the piezoelectric ceramic member 2abb on the sideremote from the vibrating member (hereinafter referred to as obverseside). For convenience, FIG. 6 shows a mirror image of the actualpattern. The pattern of obverse electrodes of the piezoelectric ceramicmember 2ab is the same as that of reverse electrodes of thepiezoelectric element member 2abb. That is, the electrode patterns ofthe piezoelectric ceramic members 2ab and 2abb superposed on each otherare equal to each other, but face in opposite directions. A manufactureprocess will now be described below. The vibrating member 1 on which theinsulator 7 is provided is the same as that of the embodiment shown inFIG. 3. Electrodes are formed on the piezoelectric ceramic members asdescribed below. Electrodes 31 to 35, and 38 to 42 (exclusive ofelectrodes 36 and 43) are formed on the reverse surface of thepiezoelectric ceramic member 2ab, and electrodes in the same pattern asthat of reverse electrodes of the piezoelectric ceramic member 2abbdisposed below are formed on the obverse surface (not shown) of thepiezoelectric ceramic member 2ab. Electrodes 45, 46, and 47 are formedon the reverse surface of the lower piezoelectric ceramic member 2abb,and electrodes 53 to 66 are formed on the obverse surface thereof incorrespondence with those of the upper piezoelectric ceramic member 2ab.At this time, the electrodes 31, 38, 45, 47, 46, 54, 53, 65, 66, 59, and60 are formed so as to be exposed at end surfaces of the piezoelectricceramic members, as illustrated. The upper piezoelectric ceramic member2ab is polarized in the direction of thickness to have oppositepolarities as indicated by (+) and (-) in FIG. 5 with respect to thereverse side. The lower piezoelectric ceramic member 2abb is polarizedin the same manner as the upper piezoelectric ceramic member 2ab, sothat the piezoelectric ceramic members 2ab and 2abb have the sameelectrode and polarization patterns. After polarization, conductivemembers 36 and 43 are formed on the reverse surface of the upperpiezoelectric ceramic member 2ab, and conductive members 67 and 68 areformed on the obverse surface of the lower piezoelectric ceramic member2abb. The electrodes 31 to 35, and 36 thereby electrically connectedform a group of reverse electrodes 37, and the electrodes 31 to 35, and36 are thereby electrically connected to form a group of reverseelectrodes 37. The other electrodes form a group of reverse electrodes44 of the piezoelectric ceramic member 2ab and groups of obverseelectrodes 69 and 70 of the piezoelectric ceramic member 2abb. Thespacing between the groups of electrodes 37 and 44 and the spacingbetween the groups of electrodes 69 and 70 correspond to 3/4 wavelengthas shown in FIGS. 5 and 6. These electrodes and conductive members are,preferably, deposited metal films having a thickness of 1 μm or less ifclose contact for bonding is considered. Then, the vibrating plate 1 onwhich the insulator 7 is formed and the piezoelectric ceramic members2ab and 2abb are bonded, and electrical connections are establishedbetween the electrodes 31 and 54, between the electrodes 45 and 53,between the electrodes 47 and 65, between the electrodes 46 and 59, andbetween the electrodes 38 and 60 by the conductive members 48 to 52.Also, by the bonding between the piezoelectric ceramic members 2ab and2abb, the unillustrated obverse electrode of the upper piezoelectricceramic member 2ab corresponding to the group of reverse electrodes 37is electrically connected to the reverse electrode 45 of the lowerpiezoelectric ceramic member 2abb, while the unillustrated obverseelectrode of the upper piezoelectric ceramic member 2ab corresponding tothe group of reverse electrodes 44 is electrically connected to thereverse electrode 46. It is thereby possible to effect electricitysupply to the group of reverse electrodes 37 of the upper piezoelectricceramic member 2ab and the group of obverse electrodes 69 of the lowerpiezoelectric ceramic member 2abb through the electrode 54, to theunillustrated obverse electrode of the upper piezoelectric ceramicmember 2ab corresponding to the group of reverse electrodes 37 and thereverse electrode 45 of the lower piezoelectric ceramic member 2abbthrough the electrode 53, to the group of reverse electrodes 44 of theupper piezoelectric ceramic member 2ab and the group of obverseelectrodes 70 of the lower piezoelectric ceramic member 2abb through theelectrode 60, and to the unillustrated obverse electrode of the upperpiezoelectric ceramic member 2ab corresponding to the group of reverseelectrodes 44 and the reverse electrode 46 of the lower piezoelectricceramic member 2abb through the electrode 59. The same operation as thatof the embodiment shown in FIG. 1 can be performed by respectivelyapplying AC voltages of V=1/4Vosinωt, V=1/4Vosin(ωt+π),V=1/4Vosin(ωt±π/2), and V=1/4Vosin(ωt±3π/2) to these electrodes. Theelectrodes 65 and 66 serve to monitor the voltage generated by vibrationof the piezoelectric ceramic element interposed between the electrodes47 and 66. Information on whether or not the piezoelectric ceramicelement is in a resonating state can be obtained from the phase andamplitude of the wave voltage corresponding to the vibration, and thiselement can be used as vibration sensor for speed control or the like.

In the embodiment of FIG. 5, two groups of electrodes (groups ofpiezoelectric elements) with a spacing corresponding to 3/4 wavelengthare provided in one piezoelectric ceramic member. Alternatively, thearrangement may be such that, as in the case of another embodiment shownin FIGS. 7 and 8, each of a pair of piezoelectric ceramic members hasone group of electrodes (group of piezoelectric elements), and that thepiezoelectric ceramic members are bonded so that their groups ofelectrodes (groups of piezoelectric elements) are shifted from eachother by λ/4 in terms of phase. In this case, as shown in FIG. 7,electrodes 101 to 111 and an electrode 113 are formed as polarizingelectrodes on the reverse and obverse surfaces of an upper piezoelectricceramic member 20ab, respectively, and the piezoelectric ceramic memberis polarized in the direction of thickness so as to have oppositepolarities as indicated by (+) and (-). The electrodes 101 and 103 areformed so as to have a terminal portion exposed at an end surface of theupper piezoelectric ceramic member 20ab, as shown in FIG. 7. conductivemembers 112 are then formed to electrically connect the electrodes 101to 111 to form a reverse electrode for driving the upper piezoelectricceramic member 20ab. The polarizing electrode 113 serves as the obverseelectrode of the upper piezoelectric ceramic member 20ab afterpolarization.

Electrodes 115 to 125 and an obverse electrode 128 are formed on a lowerpiezoelectric ceramic member 20abb, this piezoelectric ceramic member isthereby polarized, and conductive members 126 are formed thereon,thereby forming obverse and reverse electrodes in the same manner as theupper piezoelectric ceramic member 20ab. On the lower piezoelectricceramic member 20abb are further formed, as shown in FIG. 7, anelectrode 129 for electricity supply to the reverse electrode of thelower piezoelectric ceramic member 20abb, an electrode 130 forelectricity supply to reverse side of the upper piezoelectric ceramicmember 20ab, an electrode 131 for electricity supply to obverse side, anobverse electrode 132 of a vibration sensor, a reverse electrode 127 ofthe vibration sensor, and an electrode 133 for electrical connection tothe reverse electrode of the vibration sensor. The portion of thepiezoelectric ceramic member 20abb between the reverse electrode 127 andthe obverse electrode 132 is polarized in the direction of thickness.The electrodes 115, 127, 129, 130, 131, and 133 are formed so as to beexposed at an end surface of the piezoelectric ceramic member 20abb. Avibrating member 1 on which an insulator 7 is formed, the upperpiezoelectric ceramic member 20ab, an insulator 114, and the lowerpiezoelectric ceramic member 20abb are bonded so that the reverseelectrode patterns of the upper piezoelectric ceramic member 20ab andthe lower piezoelectric ceramic member 20abb are shifted from each otherby 1/4 wavelength. After this bonding, conductive members 134 to 137 areformed as shown in FIG. 8, thereby establishing electrical connectionsbetween the electrodes 129 and 115, between the electrodes 130 and 101,between the electrodes 131 and 113, and between the electrodes 133 and127. It is thereby possible to effect electricity supply to the obverseelectrode of the upper piezoelectric ceramic member 20ab through theelectrode 131, to the reverse electrode through the electrode 130, tothe obverse electrode of the lower piezoelectric ceramic member 20abbthrough the obverse electrode 128, and to the reverse electrode of thelower piezoelectric ceramic member 20abb through the electrode 129. Avibration sensor output voltage can be obtained between the electrodes132 and 133. The same operation as that of the embodiment shown in FIG.1 can be performed by respectively applying AC voltages of V=1/4Vosinωt,V=1/4Vosin(ωt+π), V=1/4Vosin(ωt±π/2), and V=1/4Vosin(ωt±3π/2) to theelectrodes 129, 128, 130, and 131. For electricity supply to theelectrodes 129, 128, 130, and 131, lead wires may be used as shown inFIGS. 1 and 2, a flexible printed circuit board may be directly bondedto the motor, or flexible printed circuit board may be bonded with ananisotropic conductive sheet conductive in the direction of thicknessalone interposed between the printed circuit board and the motor.

According to the present invention, as described above, electriccurrents can be supplied to an electrode of electro-mechanicalconversion elements, e.g., piezoelectric elements facing the bondingsurfaces of the elastic vibrating member and the piezoelectric elementswithout providing, e.g., lead wires therebetween. In particular, in acase where the elastic vibrating member and the piezoelectric elementsare insulated from each other, electric currents can be supplied toelectrodes of the piezoelectric elements with reliability while thepiezoelectric elements and the elastic vibrating member are maintainedin desired close contact with each other.

In a case where electro-mechanical conversion elements are stacked, thepresent invention also enables simple and reliable connection betweenelectrodes of the stacked electro-mechanical conversion elements.

What is claimed is:
 1. A method of making a vibration member for avibration wave driven motor comprising the consecutively performed stepsof:forming obverse and reverse electrodes on respective obverse andreverse surfaces of a piezoelectric member; forming a conductive tab onan edge of the piezoelectric member, the conductive tab beingelectrically connected to the reverse electrode; forming a reverseelectrode connector on the obverse side of the piezoelectric member;mounting a vibration member adjacent the reverse surface of thepiezoelectric member; and connecting the obverse-side reverse electrodeconnector to the conductive tab.
 2. A method according to claim 1,wherein the edge is an edge of a through-hole in the piezoelectricmember.
 3. A method according to claim 1, wherein the edge is a side endsurface of the piezoelectric member.
 4. A method according to claim 1,wherein the vibration member is electrically conductive and furthercomprising the step of mounting an intermediary insulating layer betweenthe vibration member and the reverse surface of the piezoelectricmember.
 5. A method according to claim 1, wherein said step of formingan obverse side electrode includes the consecutively performed steps offorming plural electrodes on the obverse side of the piezoelectricmember, polarizing the piezoelectric member, and connecting the pluralelectrodes to form the obverse side electrode.
 6. A method according toclaim 1, further comprising the step of mounting a similar piezoelectricmember adjacent the obverse surface of the piezoelectric member.
 7. Amethod according to claim 1, wherein the step of forming a conductivetab comprises the consecutively performed steps of imbedding aconductive rod in a block of piezoelectric material and slicing theblock of piezoelectric material into a flat piece that includes aportion of the conductive rod.
 8. A method according to claim 1, whereinthe step of forming a conductive tab on an edge of the piezoelectricmember includes forming the conductive tab on an edge of a through-holeof the piezoelectric member.
 9. A method of making a vibration memberfor a vibration wave driven motor comprising the consecutively performedsteps of:forming obverse and reverse electrodes on respective obverseand reverse surfaces of a piezoelectric member; forming a conductive tabon a predetermined portion of the piezoelectric member, the conductivetab being electrically connected to the reverse electrode; forming areverse electrode connector on the obverse side of the piezoelectricmember; mounting a vibration member adjacent the reverse surface of thepiezoelectric member; and connecting the obverse-side reverse electrodeconnector to the conductive tab.
 10. A method according to claim 9,wherein the predetermined portion is an edge of a through-hole in thepiezoelectric member.
 11. A method according to claim 9, wherein thepredetermined portion is a side end surface of the piezoelectric member.